From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262273AbTHSHZs (ORCPT ); Tue, 19 Aug 2003 03:25:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262439AbTHSHZs (ORCPT ); Tue, 19 Aug 2003 03:25:48 -0400 Received: from 81-2-122-30.bradfords.org.uk ([81.2.122.30]:37504 "EHLO 81-2-122-30.bradfords.org.uk") by vger.kernel.org with ESMTP id S262273AbTHSHZr (ORCPT ); Tue, 19 Aug 2003 03:25:47 -0400 Date: Tue, 19 Aug 2003 08:37:31 +0100 From: John Bradford Message-Id: <200308190737.h7J7bVaa000623@81-2-122-30.bradfords.org.uk> To: herbert@13thfloor.at Subject: Re: [OT] Documentation for PC Architecture Cc: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > > I've done some tests with a simple kernel which I wrote: all that region > > (except video memory at 0xb8000) results "read only"... > > because it is usually designated as rom area, which naturally > is read only ... On some boards I've seen, there is 384K onboard for ROM shadowing purposes, and when only 128K is actually used, (as it is in a lot of configurations), the other 256K is available as system memory. However, this on-board 256K is only remapped when you have 8 MB RAM or less on the board. So with 8 MB the board reports 8448K of RAM, but with 16 MB, it only reports 16384K. In that case 256K of real RAM is, indeed, lost. John.